https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70594
--- Comment #5 from Patrick Palka <ppalka at gcc dot gnu.org> --- (In reply to Tobias Burnus from comment #4) > Created attachment 38225 [details] > test.ii test case (g++ -O1 -fcompare-debug) > > (In reply to Jakub Jelinek from comment #1) > > Without the testcase it is hard to guess. > > I now tried to compile LLVM with -fcompare-debug - and I guessed correctly, > one of the files also fails there (lib/Support/CommandLine.cpp). > > I am not sure whether it is the same issue, but it is a debug miscompare. > Contrary to my original file, it also fails when a .ii is generated with > "-E"; additionally, it also fails already with -O1 and it reduced more > readily (for my original example, it seemed to depend much more on the > memory layout such that comment lines were kept). > > The somewhat reduced example is attached; it fails here (and hopefully > elsewhere) using "g++ -O1 -fcompare-debug" with: "g++: error: test.ii: > -fcompare-debug failure". Same here. Some observations: Reverting the portion of the patch that added the "deletable" GTY tag to constexpr_call_table fixes the failure. Making get_fundef_copy() to always allocate a new function (thus making it as if the fundef_copies_table didn't exist) doesn't fix the failure. So it seems that adding the "deletable" GTY tag to constexpr_call_table is responsible for this regression, and not the new fundef_copies_table. Still have no idea why or how though.
